Surface materials for decontamination with decontaminants

ABSTRACT

Reversibly switchable (transformable) surface layer changeable from (super)hydrophobic to (super)hydrophilic surface states are described. Methods of decontamination of surfaces exposed to contaminate are provided. The reversibly switchable properties of the surface layer can be controlled by an external stimulus.

TECHNICAL FIELD

This disclosure relates to decontamination methods and surfacesconfigured for decontamination, and in particular to methods of andmaterials for using a surface adjustable upon application of an externalstimulus.

BACKGROUND

Decontamination of biological and/or chemical agents is necessary incurrent environments. Biological decontamination is the deactivationand/or destruction of microorganisms, and pathogens, such as bacteria,both vegetative and sporulative, bacterial spores, viruses, mycoplasma,protozoans, oocysts, and toxins. Chemical decontamination is thedeactivation and/or destruction of chemical contaminants, pesticides,chemical warfare agents, and other toxic substances. Some conventionalmethods of decontamination, of surfaces, which may also includedisinfecting agents, include chemical washing, fumigation, heattreatment, and irradiation. Chemical washing includes washing thesurface with simple soap and water, bleach, DS-2, hydrogen peroxide,alkali, hexachlorophene, quaternary amines, and the like. Fumigationincludes exposing an object or its surface to a fumigant for a timesufficient to deactivate or destroy the biological/chemical agent. Heatand irradiation treatments involve providing temperatures or amounts ofradiation, respectfully, that is fatal to the biologic or sufficient todecompose or alter the chemical substance to one that is not harmful.

In certain situations, it may be necessary to decontaminate a vehicle,for example, an aerospace vehicle, which has been contaminated for oneor more reasons. “Contaminated” interior aircraft surfaces are typicallydecontaminated by application of fluid decontaminants. The methods forapplying the liquid decontaminant include hand-wiping, or controlledapplication using sprayers, or injectors, nebulizers or atomizers. Ineach of these processes there is an implicit trade-off between (i)creating a decontaminating fluid layer that covers the affected surfacewell and also penetrates into grooves and crevices (e.g., surfaceshaving complex geometries); and (ii) removing completely thedecontaminating fluid and biological/chemical agent from the surfacesand crevices, while minimizing and/or preventing surface damage andcorrosion to the aerospace vehicle. Conventional washing methods andaerosolized decontamination use surfactants that may reduce the surfacetension of surfaces, however such methods delay the removal of fluidand/or may leave residues. Likewise, fumigation methods often result innon-uniform coverage, with the decontaminating agents depositing incoalesced droplets, rather than in a fluid film, resulting in reduceddeactivation or destruction of the biological/chemical agent and/oroverall reduced efficacy of the decontamination process. Known chemicalagent resistant surfaces and/or coatings typically require applicationof caustic oxidizing solutions to remove any chemical or biologicalagents or contaminants. Such caustic oxidizing solutions, such as DS2(Decontamination Solution Number 2), which comprises 70%diethylenetriamine, 28% ethylene glycol monomethyl ether, and 2% sodiumhydroxide, can cause damage to surfaces and surroundings to which it isapplied. Moreover, having to transport such additional caustic oxidizingsolutions to the location of the contaminated aircraft, rotorcraft,vehicle, or equipment can be expensive and time consuming. In addition,having to apply such additional caustic oxidizing solutions can be timeconsuming and labor intensive, and the down time of the aircraft,rotorcraft, vehicle, or equipment can be increased.

SUMMARY

In a first embodiment, a method for decontaminating a surface isprovided. The method comprising: providing a surface susceptible tocontamination, the surface having a first hydrophobic surface state anda second hydrophilic surface state, wherein the first surface state andthe second surface state are reversibly transitionable by application ofan external stimulus; optionally, introducing a decontaminating agent tothe contaminated surface; and transitioning at least a portion ofsurface such that the decontaminating agent wets at least a portion ofthe surface. In one aspect, at least a portion of the surface of thesubstrate is decontaminated.

In a first aspect, the method further comprises removing at least aportion of the decontaminating agent from the surface.

In another aspect, alone or in combination with the first aspect, thestimulus is electrical, light, chemical, mechanical, or combinationsthereof.

In another aspect, alone or in combination with any one of the previousaspects, the decontaminating agent substantially wets the hydrophilicsurface.

In another aspect, alone or in combination with any one of the previousaspects, the hydrophobic surface is superhydrophobic.

In another aspect, alone or in combination with any one of the previousaspects, the hydrophilic surface is superhydrophilic.

In another aspect, alone or in combination with any one of the previousaspects, the hydrophilic surface facilitates liquid film formation ofthe one or more decontaminating agents.

In another aspect, alone or in combination with any one of the previousaspects, the method further comprises removing at least a portion of theone or more contaminates.

In another aspect, alone or in combination with any one of the previousaspects, the substrate is at least an interior surface of a vehicle orthe exterior surface of equipment.

In another aspect, alone or in combination with any one of the previousaspects, the substrate is at least an interior surface of an aerospacevehicle.

In a second embodiment, an apparatus is provided. The apparatuscomprises: at least one reversible surface, reversible by application ofan external stimulus from a first surface state to a second surfacestate, wherein: (i) the first state presents a substantially hydrophobicsurface and the second state presents a substantially hydrophobicsurface; or (ii) the first state presents a substantially hydrophobicsurface and second state a substantially hydrophobic surface wherein thefirst surface state is at least partially restored upon removal of theexternal stimulus.

In a first aspect, the at least one reversibly surface comprises asemiconductor oxide or chemically modified polymer.

In another aspect, alone or in combination with the first aspect, thesurface is at least a portion of the interior of an aerospace vehicle.

In a third embodiment, a method for decontaminating a surface isprovided. The method comprises providing a surface susceptible tocontamination, the surface having a first surface state and a secondsurface state, wherein the first surface state and the second surfacestate are reversible by application of an external stimulus; whereineither (i) the first surface state presents a substantially hydrophobicsurface and the second surface state presents a substantiallyhydrophobic surface; or (ii) the first surface state presents asubstantially hydrophobic surface and second surface state presents asubstantially hydrophobic surface; introducing a decontaminating agentto the surface; and adjusting at least a portion of the first surfacestate to the second surface state, wherein the decontaminating agentwets at least a portion of the surface.

In a first aspect, the method further comprises discontinuing theexternal stimulus, wherein at least a portion of the second surfacestate is reversed back to the first surface state.

In another aspect, alone or in combination with the first aspect, thesecond surface state facilitates wetting of at least a portion of thesurface layer by the decontaminating agent.

In another aspect, alone or in combination with any of the previousaspects, the wetting of the surface layer facilitates decontamination ofthe surface.

In another aspect, alone or in combination with any of the previousaspects, the surface comprises semiconductor oxides or chemicallymodified polymer.

In another aspect, alone or in combination with any of the previousaspects, at least a portion of the hydrophobic surface state is asuperhydrophobic surface.

In another aspect, alone or in combination with any of the previousaspects, at least a portion of the hydrophilic surface state is asuperhydrophilic surface.

In another aspect, the method further comprising removing at least aportion of the contamination from the contaminated surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a flow chart of an exemplary method disclosed herein.

FIG. 2 illustrates the reversible wetting of an adjustablehydrophobic-hydrophilic surface.

FIGS. 3A-3D depicts an exemplary embodiment of the materials and methodsdisclosed herein for decontamination of a surface.

FIG. 4 depicts an alternate exemplary embodiment of the materials andmethods disclosed herein for decontamination of a surface.

FIG. 5 depicts another exemplary embodiment of the materials and methodsdisclosed herein for decontamination of a surface.

FIG. 6 depicts another exemplary embodiment of the materials and methodsdisclosed herein for decontamination of a surface.

DETAILED DESCRIPTION

The present disclosure related to reversibly adjustable, ortransformable, materials for protecting against contamination and/orenabling effective decontamination dynamically with application of anexternal stimulus. Such surfaces or surface-adjustable coatings can beused on equipment existing or interiors of vehicles. Such surfaces orcoatings preferably maintain their adjustability in severewear-intensive environments. Such adjustable coatings can be applied ontop of a painted surface, a fabric, or other surface used on or invehicles, or equipment. Such surfaces or coatings reduce the amount ofchemical (decontaminating agents) required and/or shorten thereturn-to-service time to decontaminate the equipment or vehicle. Suchsurfaces and coatings are adapted for use with conventional hazmat anddecontamination techniques and can be readily incorporated with suchmethods.

The process and materials disclosed herein are is particularly suitedfor the decontamination of surfaces pertaining to equipment, andoccupiable volumes or spaces in need thereof as a result of acontamination event.

(Super)Hydrophobic and (Super)Hydrophillic Surfaces

The terms “hydrophobic” and “hydrophilic,” in relationship to surfaces,have their ordinary and customary meaning as used herein.Superhydrophobic surfaces are highly hydrophobic, i.e., extremelydifficult to wet. For example, the contact angle of a water droplet on asuperhydrophobic surface exceeds 150° and the roll-off angle is lessthan 10°.

Superhydrophilic surfaces are characterized as providing extremely lowcontact angle between water and the surface. The contact angle of waterwith generally hydrophilic inorganic materials, such as glass, isgenerally 20-40 degrees, whereas the contact angle of water with typicalhydrophilic organic materials, such as resins, is 70-90 degrees, and thecontact angle of water with hydrophobic resins, such as silicone resinand fluorocarbon polymers, is more than 90 degrees. By way ofcomparison, the contact angle of superhydrophilic surfaces is less than20 degrees, less than 10 degrees, or less than 5 degrees. In someaspects, a superhydrophilic surface can cause the water contact angle toapproach zero.

Contact angle is a measure of static hydrophobicity, and contact anglehysteresis and slide angle are dynamic measures useful for determiningthe state of the surface of the disclosed embodiments. Contact anglehysteresis is a phenomenon that characterizes surface heterogeneity.Differences between advancing and receding contact angles, termedcontact angle hysteresis, can be used to characterize surfaceheterogeneity, roughness, and mobility. Surfaces that are nothomogeneous will have domains which impede motion of the contact line.The slide angle is another dynamic measure of hydrophobicity and ismeasured by depositing a droplet on a surface and tilting the surfaceuntil the droplet begins to slide.

The present method provides, in one aspect, an adjustable substratesurface having a first hydrophobic surface state that transitions to asecond hydrophilic surface state promoting uniform coverage with a fluidfilm comprising one or more water-based decontaminant, which maximizesdecontamination of the substrate. After decontamination, the substratesurface state can be transitioned back to the first hydrophobic surfacestate that promotes aggregation of the fluid into droplets that can beremoved easier.

The effect of hydrophobic/hydrophilic transitional properties of thesurface is beneficial for the decontaminating agent such as where forwater-based decontaminant fluids, the second hydrophilic surface statepromotes essentially a uniform coverage with a fluid film (e.g.,wetting), which enhances decontamination, and the first hydrophobicsurface state promotes aggregation of fluid into droplets that can beremoved easier, since they will coalesce and/or tend to roll off thesurface. In another aspect of the present method, an adjustablesubstrate surface having a first hydrophilic surface state thattransitions to a second hydrophobic surface state is beneficial forutilization of one or more emulsion-type decontaminant that is at leastpartially hydrophobic, and thus, the one or more emulsion-typedecontaminates will form a film on the second hydrophobic surface, andupon transition back to the first hydrophilic surface state provide forremoval of the emulsion-type decontaminate.

Adjustable surfaces switching reversibly between hydrophobic andhydrophobic surface states can be effectively fabricated by utilizingstimuli-responsive materials. Such surfaces in combination withdecontaminating agents provide a method of decontaminating vehiclesand/or equipment. The surfaces can be prepared with materials added toengineering materials used to fabricate the vehicle or equipment or canbe coated on existing interiors and/or surfaces of the vehicle orequipment. In one aspect, adjustable surfaces switching reversiblybetween super-hydrophobic and super-hydrophilic surface states can beemployed. The surface states can be adjusted by the application of anexternal stimulus, whereas discontinuation or modulation of the externalstimulus reversibly adjusts the surface of the substrate between thefirst state and second state. The external stimulus can be directed tothe materials directly or the interior they are coated on. In thismanner, the decontamination can be more efficient, as the surfacecontaminate is more effectively presented to the decontaminating agentsand or more easily removed from the contaminated surfaces. Moreover,contamination that has entered small crevices or surface defects is moreefficiently presented to the decontaminating agents upon adjustment ofthe substrate surface from a first hydrophobic surface state to a secondhydrophilic state.

The externally applied stimulus can includes one or more of lightirradiation, electrical potential, temperature, pH or selected solvents,and/or mechanical forces. Such adjustable surfaces include controllable,wettable surfaces that are configured to receive and/or interact withdecontaminating agents and other compounds effective in decontamination.

Materials and Methods of Adjusting Surface States

Examples of adjustable materials for the methods disclosed hereininclude, for example, photo-responsive materials, include inorganicsemiconductor oxides such as titania, zinc oxide, vanadium oxide, etc.These materials are normally hydrophobic in a first state, and can bemodified, e.g., by texturing to a submicron roughness, to provide afirst superhydrophobic surface state. Exposure of the semiconductoroxide surfaces to UV light provides for an adjustment or transition ofthe surface to a second hydrophilic surface state, which if modified bysubmicron roughness can provide essentially complete wetting of aqueousmedia alone or in combination with decontaminating agents. Storage ofthe second hydrophilic state in the dark for a sufficient time intervalprovides for reversibility from the second state to the first state.

The adjustable materials or coatings can include one or more of oxidesof titanium, oxides of zinc, oxides of iron, oxides of silver, oxides ofcopper, oxides of tungsten, oxides of tin, oxides of bismuth, strontiumtitanate and mixtures thereof. The oxides in the adjustable materials orcoatings can include sub-oxides, stoichiometric oxides, andsuper-oxides. In embodiments, the ultraviolet radiation activated layerincludes one or more of TiO₂, ZnO, Fe₂O₃, WO₃, SnO₂, Bi₂O₃, V₂O₅, andSrTiO₃. The oxides can be used in a form that is suitable forincorporation into materials to affect the surface thereof, or used incoatings. The oxides can be of a size suitable for such applications,including micron particles, submicron particles, nanoparticles, andphysical mixtures and/or distributions thereof. Preferably, theadjustable materials or coatings include titanium oxide or vanadiumoxides. Preferably, the titanium oxide includes TiO₂. The titanium oxidecan include amorphous, rutile and anatase phases of titanium oxide, or amixture of two or more of these phases.

The inorganic semiconductor oxides can be added to materials normallyused in the fabrication or construction of vehicles or equipment,especially interiors of vehicles. Preferably, the inorganicsemiconductor oxides are more concentrated at the surface, which can beprovided by molding techniques or post-fabrication annealing.Alternatively, the inorganic semiconductor oxides can be deposited onexisting surfaces of the vehicles or equipment, for example, by sputtercoating, thermal spraying, or other coating techniques.

Additional compounds, either as additives, surface graphs, or coatingscan be used alone or in combination with the above inorganicsemiconductor oxides. Such additional compounds can be organic orsubstantially organic, for example, azobenzene and spiropyran functionalgroups, capable of switching between polar forms in response to lightand switching back to a nonpolar form after a predetermined time in thedark.

In another aspect, adjustable materials or coatings useful forpracticing the methods herein disclosed can be reversibly electricallyinduced between different surface states. Such adjustable materials orcoatings include conducting polymers, for example, a positively chargedconjugated (alternating single and double bond) backbone polymer incombination with negatively charged dopants. Thehydrophobicity/hydrophilicity can be controlled by the selection ofconducting polymer and type of dopant and the dopant concentration. Inone example, polypyrrole (PPy) films on submicron roughened surfaces canbe adjusted from a (super)hydrophobic to (super)hydrophilic state byadjusting the applied voltage to the adjustable material or coating, orthe grounded vehicle or equipment.

In yet another aspect, adjustable surface can be reversed by applicationof an amount of heat or thermal radiation sufficient to effect thetransition of the first hydrophobic surface state to the secondhydrophilic surface state. Exemplary adjustable materials or coatingsthat can be reversibly thermally adjusted between a first hydrophobicsurface state and a second hydrophilic surface state include polymericsystems and surface coatings. For example, chemically modifiedpoly(N-isopropylacrylamide) combined with surface roughness, hasexcellent reversibility between a first hydrophobic state at about at20° C. and a second hydrophilic state at about 40° C., respectively. Insome aspects, reversibility between a hydrophobic surface and ahydrophilic surface can, in part, be manipulated by the roughness of thesurface. For example, the roughness-enhanced thermally responsivewettability of a poly(N-isopropylacrylamide) (PNI-PAAm)-modified surfaceprovides for reversible switching between a first superhydrophilicsurface state and a second superhydrophobic surface state in a narrowtemperature range of about 10° C. While not to be held to any particulartheory, this transition is believed to result from the combined effectof the chemical variation of the surface and the surface roughness. Suchsurfaces may be prepared by surface-initiated atom-transfer radicalpolymerization to fabricate thermally responsive PNI-PAAm thin films,for example, on both flat and textured substrates.

In yet another aspect, exemplary surfaces and coatings useful inpracticing the methods herein disclosed include materials that canadjust from a first hydrophobic surface state and a second hydrophilicsurface state by way of geometric control of the surface and/or theintroduction of stress to the surface. Thus, applying a mechanicalstress to a micro/nanostructured surface effectuates a change thespacing and/or geometry of surface features, such as asperities in oneor more physical dimensions. Roughness (projected area/actual area) canbe adjusted to change one or more feature aspect ratios so as to controlthe nature of the hydrophobic/hydrophilic adjustment. For example, afirst geometric-shaped hydrophobic surface state can be stimulated tochange to a second geometric-shaped hydrophilic surface state under astress. The stress can be uni-axial or biaxial relative to the surfaceof the substrate or coating. In one aspect, the coating or surface in afirst unstretched state is hydrophobic or superhydrophobic and adjustsor transforms to a second stretched state that is hydrophilic orsuperhydrophilic when stretched. In one aspect, the polymer is apolyimide with a predetermined side chain configuration of predeterminedlength and/or chemical composition that allows wetting in the second thestretched-strained state by providing the wetting fluid access to alower energy state as opposed to a higher energy state that forces orrepeals the wetting fluid in the (super)hydrophobic “Cassie” state.

The process disclosed herein is adaptable for treating chemical and/orbiological contamination of a surface, such as a surface interior of avehicle, such as an aerospace vehicle or other vehicle or equipment.

In one exemplary embodiment, a photo-adjustable material is used toexemplify the methods herein disclosed, for which substitution of theappropriate stimulus being readily undertaken by one of ordinary skill.Generally, a decontaminating agent is applied to the surface, preferablyas an aerosol spray, whereby the surface having previously been orsubsequently illuminated, preferably with ultraviolet light, withsufficient intensity (power per unit area) to effect adjustment of thesurface from the first hydrophobic surface state to the secondhydrophilic surface state to receive the decontamination agent. Thisdecontamination can result from the photodecomposition of the chemicalcontaminants or alteration of critical biological molecules orstructures of the pathogens, and/or result in chemical reaction with theproducts of photochemical reactions to effect the decontamination ordeactivation. The surface state can be reversed back to one ofhydrophobic or superhydrophobic to facilitate the removal of thecontaminates, which can be viable or partially or completelydeactivated.

Thus, in one example, an adjustable surface suitable for UV stimulationcan be a semiconductor oxide, suitable for exposure of UV having asurface thickness on a substrate of from about 1 to about 250 nm,preferably from 14 to 20 nm, thick. UV activation can be accomplished byexposure to sunlight or UV radiation having a wavelength in a range offrom 10 to 400 nm, e.g., from 300 to 400 nm. UV radiation having awavelength of 350 to 400 nm can be used for adjusting materials orcoating comprising, e.g., TiO₂. The ultraviolet radiation activatedlayer can generally be activated with a minimum dose of UV radiation ina range of from about 0.001 to 1 mW/cm². Other intensities can be used.

One or more decontaminating agent during the illumination of theadjustable surface while in or subsequent to the second hydrophilicstate so that a sufficient quantity of decontaminating agent isavailable to contact the contaminants and/or pathogens. According to oneaspect, the decontaminating agent(s) can be electrostatically charged(e.g., as it is sprayed as an aerosol) to promote the adherence of theagent to the surface to be treated. For conducting or semiconductingtargets, or dielectric targets that are backed by conductors or haveconductors within their structure, the charged particles resulting fromthe electro-spraying will be attracted to, and adhere to, the surface tobe treated.

In another exemplary embodiment, a thermally-adjustable material is usedto exemplify the methods herein disclosed, for which a thermal systemcan be employed to raise the temperature of the substrate, which can bethe interior surfaces of a contaminated vehicle or equipment. Thethermal decontamination system is configured to deliver heated or cooledair under feed-back control from a self contained unit, which can bemobile, e.g., on a truck. The system is intended to deliver hot air ofcontrolled humidity to achieve transition of the first hydrophobicsurface state to the second hydrophilic surface state whiledecontaminating agents are introduced. Viral and/or chemicaldecontamination can also occur by heat exposure. The second hydrophilicsurface state is then cooled so as to return to first hydrophobicsurface for re-entry and/or use the vehicle or equipment.

Another example, which can be used in combination with any of thematerials previously discussed, is a biomimetic surface includes astructure similar to that found in nature, comprising asurface-structured polymer, such as polycarbonate, polyamide or otherengineering resins. The polymer comprises a micro/nano binary structuresimilar to a natural micro/nanostructure, e.g., that of a lotus leaf.These nanoscale features enhance the polymer surface's hydrophobicity,with or without the combination of the materials discussed above.

Decontaminating Agents

The decontaminating agent can be a fluid, a gas, or a solid dissolved orsuspended in a fluid carrier. Decontaminating agent chemistry can bechosen based on its effectiveness for destruction/inactivation of theparticular biological and chemical agents, preferably agents are safe tothe components of the vehicle and/or equipment interior components, forexample. As used herein, contacting the surface with a fluid or gas, thefluid or gas having one or more decontaminating agents effective againstone or more contaminates is inclusive of any amount ofdestruction/inactivation of the particular biological and/or chemicalagent, or the encapsulation of the particular biological and/or chemicalagent for safe removal. Destruction includes the death of a biologicalagent or the biological alteration thereof to a non viral or non-toxicstate or form. Inactivation includes chemical alteration of the chemicalagent to a non-toxic or harmless compound.

Examples of suitable non-toxic decontaminants include peracids, such asperacetic acid, halogen solutions, halogen compounds and solutions ofhalogen compounds (e.g., sodium hypochlorite, chlorhexidine digluconate,cetyltrimethylammonium, -benzylammonium, and -diammonium halides,cetyltributylphosphonium halides, dodecyltrimethylammonium halides,tetradecyltrimethylammonium halides, and the like), phenolic compoundsand halogenated phenolic compounds in solution (e.g., Triclosan),selenium sulfide, asiatic acid, benzoyl peroxide, minocyclin, and thelike, alone or in combination. A peracetic acid solution, at aconcentration of about 500 to about 5000 ppm optionally with surfactantsto aid removal of the contamination, is suitable and is effectiveagainst a large number of chemical and biological pathogens. In additionto the decontaminating agent, sensitizers, e.g., photosensitizers,surfactants, wetting agents, etc., can be used.

Photosensitizers can be chosen based on a preferred microbicidal orchemical decontamination protocol, e.g., photooxidative, photocytotoxicor photodynamic reactions. For broad spectrum microbicidal effect,photooxidative photosensitive effects can be used. Suitablephotosensitizers include mixtures of peroxy compounds, for example,peroxy compounds comprising an —OH or an —OOH group, including hydrogenperoxide, paracetic acid, hydrogen peroxide and paracetic acid,perpropioniac acid, propionic acid, and mixtures thereof. One suitablephotosensitizer is an aqueous solution containing about 0.01% to about1% peracetic acid sold as ZEROTOL© available from Bio-Safe System, Inc.,or RENALIN© available from Minntech Corp.

A surfactant may be added to decontaminating agents to aid in thedispersion and coating of the surface in the second hydrophilic state.The selection of the surfactant depends upon the nature of the surface,the biological/chemical contaminant and/or its action as a wetting agentand its non-interference on the decontamination effect of thedecontaminating. Suitable surfactants include non-ionic surfactants suchas low carbon number alcohol ethoxylate, anionic surfactants, includingalkyl sulfates and alkane sulfonates, and mixtures thereof. For example,alkyl sulfates and alkane sulfonates can be used. Various diluents canbe added to adjust the viscosity or concentration of the decontaminatingagents, or to stabilize the decontaminating agents. The selection of thediluent depends upon the environmental conditions and the deliverysystem. Suitable diluents include water and weaker acids. Wetting anddispersion on the surface of an object can be aided by use of asurfactant. Selection of surfactant depends on.

With reference to FIG. 1, a block diagram depicting in a general sensethe disclosed method is provided. Thus, Step 100 provides a substratehaving a first surface state, which can be hydrophobic or hydrophilic.Step 110 provide for the application of a stimulus to the adjustablesurface, causing the first surface to transition, e.g., to hydrophilicor hydrophobic, (the “opposite”) respectively, which can be sequentialor simultaneous with Step 150, the introduction of the decontaminatingagent to the particular adjusted surface state, as shown by dotteddouble arrow cycle 150, whereby the decontaminate, having hydrophobic orhydrophilic characteristics, can form a film on the second surfacestate. Cycling of steps 110 (including the stimulus) and 120 (includingvarying amounts of agent introduction) can be used as needed. After atime interval known or predetermined to provide decontamination of thecontaminated surface, the application of stimulus is discontinued,terminated, or otherwise ended, as in Step 130. Termination of thestimulus reverts the second surface state back to the first surfacestate and facilitates the removal, e.g., by beading up, of thedecontaminate and optionally, the contaminate. Steps 110, 120 and 130can be cycled any number of times as needed. Step 140 depicts theoptional removal of at least a portion of the decontaminating agentsfrom the surface of the substrate, for example by wiping, vacuum,evaporating, etc., and/or at least a portion of the contaminates. Steps110, 120, 130, and 140 can be cycled any number of times as needed. Inone aspect, the substrate surface is designed for one cycle, forexample, the adjustment from the first state to the second state,whereby the decontamination is completed and the substrate surface isreplaced. In other aspects, the substrate surface is returned to normalor similar service.

FIG. 2 depicts in general the reversibility of the first and secondsurface states and the effect on wetting. Thus, substrate 200 havinghydrophobic (or hydrophillic) surface 205, which is in the first state,displays characteristic beading of aqueous droplet 300. Adjustment ortransformation by stimulus, indicated by arrow 500, provides alteredsecond surface state 207, displaying characteristic wetting behavior ofaqueous droplet 305. Removal of stimulus, which can be electrical, lightenergy, heat energy, or mechanical stress, causes reversal ofessentially all or part of surface 207 to convert, transform, or adjustback to first hydrophobic (or hydrophilic) state, e.g., surface 205.While exemplary, FIG. 2 can be representative of asuperhydrophobic-superhydrophilic surface state transition oradjustment.

FIG. 3A depicts one embodiment of the method disclosed herein wherein acontaminated surface is decontaminated. Thus, substrate 200 havinghydrophobic (or hydrophilic) surface 205, which is in the first date,further having contaminant 400 present thereon, is presented withdecontaminating agent 300. FIG. 3B depicts adjustment or transition fromthe first hydrophobic (or hydrophilic) surface state to a secondhydrophilic (or hydrophobic) surface state, depicted as surface 207,whereby decontaminating agent 300 has wetted surface 207 and contaminant400 is either deactivated, chemically altered, or both as depicted bythe generic “deactivated contaminant” 405. In one aspect, deactivatedcontaminant 405 may still be viable. FIGS. 3C-3D depict adjustment ofthe second hydrophilic (or hydrophobic) surface state back to the firsthydrophobic (or hydrophilic) surface state (shown by arrow 550), wherebysurface 205 causes decontaminating agent 305, which contains deactivated(or viable) contaminant 405, is presented for removal. In an alternateembodiment, contaminate 405 is left on the surface in a deactivated ordetoxified state.

FIG. 4 presents an alternate embodiment of the methods described herein,whereby surface of substrate is configured with asperities having alength 605 along the longitudinal axis of the surface, and having aheight 607 perpendicular to the longitudinal axis of the surface ofsubstrate 225. Contaminant 400 may be present in crevices or cracks 230in the surface of substrate 205. Decontaminating agents 300 arepresented to substrate to 225 after adjustment of surface 205 to thesecond hydrophilic (or hydrophobic) surface state, depicted as surface207. Decontaminating agents 305 wets the surface 207, which maydeactivate or chemically alter contaminant 405. Adjustment of the secondhydrophilic surface state 207 back to first hydrophobic (or hydrophilic)surface state (e.g., by removing stimulus as depicted by arrow 585)presents decontaminating agent 305 and deactivated contaminant 405 forremoval.

FIG. 5 depicts an alternative method herein disclosed similar to that asdepicted in FIG. 4 except that adjustment or transition state, asdepicted by arrow 725, is performed prior to introduction of thedecontaminating agent 300. Thus, in this aspect, contaminant 400 is moreefficiently presented to decontaminating agent 300 on second hydrophilic(or hydrophobic) surface state depicted by surface 207. Wetting ofdecontaminating agent 305 on surface 207 facilitates removal ofdeactivated contaminant 405 as shown by dotted arrow 750.

FIG. 6 depicts an alternate method herein disclosed similar to that ofFIG. 5 (that can alternatively be that of FIG. 4), but for deactivatedcontaminate 405 b remaining on the surface of the substrate afterreversal to the first surface state. Decontaminating agent 300 can beremoved or left on surface 205 e.g., left to evaporate or sublime and/orbe physically removed alone or in combination with contaminate 405 or405 b.

As discussed above, reversible hydrophobic/hydrophilic surfaces can beilluminated with a UV light. A UV light unit may be a hand-held, pulsedUV lamp system, such as a short-arc-bulb flashlamp array. The UV lightunit can be placed in close proximity to the surface to facilitate theadjustment of the surface from the first surface state to the secondsurface state. The adjustable surface when in the second hydrophilicsurface state can be contacted with one or more decontaminating agents.In one aspect, the decontaminating agent when contacting the secondhydrophilic surface state effectively removes substantially all of thecontamination. In other aspect, the UV light, alone or in combinationwith the second hydrophilic surface state and decontaminating agentand/or sensitizers, surfactants, etc., can deactivate the contaminate.Exposures of less than 105 J/m² can effect several orders of magnitudedeactivation of most pathogens.

In one aspect, a mobile system is used to provide the UV light and/orthermal energy to facilitate the surface adjustment of the substrate tobe decontaminated. The mobile unit can be configured for deployment inan aerospace vehicle, for example, a unit having a UV light intensity ofabout 1 to 1000 mW/cm² or IR heat. The light source can be continuous orpulsed. The mobile system can further comprise a spraying system fordispensing the decontaminating agents. The sprayer system and the UV orIR light system can be operated remotely, or manually operated, forexample by personnel wearing protective clothing, protective eyeglasses,goggles, masks and/or respirator apparatus as may be necessary.Furthermore, the personnel can be provided with, and garments to avoiddamage to their eyes or skin by prolonged exposure to UV light.

Typically, the time required for decontamination is proportional to theamount of contaminating substance present. The decontamination time isalso a function of the time required for the first hydrophobic surfacestate to adjust to the second hydrophilic surface state, decontaminatingagent and/or the specific stimulus (e.g., wavelength of UV lightapplied, and the flux intensity of light) used and applied.

The methods and apparatus of the present invention can be used inemergency and military applications to decontaminate vehicles, clothedand unclothed persons, tools and implements, and airborne clouds createdby chemical and biological weapons, and industrial accidents.

From the foregoing description, various modifications and changes in thecompositions and method will occur to those skilled in the art withoutvarying from the scope of the invention as defined in the followingclaims.

1. A method comprising: applying an external stimulus to a surface of asubstrate, adjusting at least a portion of the surface from a firststate to a second state, wherein either (i) the first state presents asubstantially hydrophobic surface and the second state presents asubstantially hydrophilic surface; or (ii) the first state presents asubstantially hydrophilic surface and second state presents asubstantially hydrophobic surface; contacting the surface in the secondstate with a fluid or gas, the fluid or gas having one or moredecontaminating agents effective on one or more contaminates associatedwith the surface of the substrate; removing the external stimulus to thesurface of the substrate, the surface transforming from the second stateback to the first state, whereby at least a portion of the surface ofthe substrate is decontaminated.
 2. The method of claim 1, furthercomprising removing at least a portion of the decontaminating agent fromthe surface.
 3. The method of claim 1, wherein the stimulus iselectrical, light, chemical, mechanical, or combinations thereof.
 4. Themethod of claim 1, wherein by the decontaminating agent substantial wetsthe hydrophilic surface.
 5. The method of claim 1, wherein thehydrophobic surface is superhydrophobic.
 6. The method of claim 1,wherein the hydrophilic surface is superhydrophilic.
 7. The method ofclaim 1, wherein the hydrophilic surface facilitates liquid filmformation of the one or more decontaminating agents.
 8. The method ofclaim 1, further comprising removing at least a portion of the one ormore contaminates.
 9. The method of claim 1, wherein the substrate is atleast an interior surface of a vehicle or the exterior surface ofequipment.
 10. The method of claim 1, wherein the substrate is at leastan interior surface of an aerospace vehicle.
 11. An apparatuscomprising: at least one reversible surface reversible by application ofan external stimulus from a first surface state to a second surfacestate, wherein either (i) the first surface state presents asubstantially hydrophobic surface and the second surface state presentsa substantially hydrophilic surface; or (ii) the first surface statepresents a substantially hydrophilic surface and second surface statepresents a substantially hydrophobic surface, the first surface statebeing at least partially restored upon removal of the external stimulus.12. The apparatus of claim 11, wherein the at least one reversiblysurface comprises a semiconductor oxide or chemically modified polymer.13. The apparatus of claim 11, wherein the surface is at least a portionof the interior of an aerospace vehicle.
 14. A method fordecontaminating a surface, the method comprising: providing acontaminated surface, the contaminated surface having a first surfacestate and a second surface state, wherein the first surface state andthe second surface state are reversible by application of an externalstimulus; wherein either (i) the first surface state presents asubstantially hydrophobic surface and the second surface state presentsa substantially hydrophilic surface; or (ii) the first surface statepresents a substantially hydrophilic surface and second surface statepresents a substantially hydrophobic surface; introducing adecontaminating agent to the contaminated surface; and adjusting atleast a portion of the first surface state to the second surface state,wherein the decontaminating agent wets at least a portion of thesurface.
 15. The method of claim 14, further comprising discontinuingthe external stimulus, wherein at least a portion of the second surfacestate is reversed back to the first surface state.
 16. The method ofclaim 14, wherein the second surface state facilitates wetting of atleast a portion of the surface layer by the decontaminating agent. 17.The method of claim 14, wherein the wetting of the surface layerfacilitates decontamination of the surface.
 18. The method of claim 14,wherein the surface comprises semiconductor oxides or chemicallymodified polymer.
 19. The method of claim 14, wherein at least a portionof the hydrophobic surface state is a superhydrophobic surface.
 20. Themethod of claim 14, wherein at least a portion of the hydrophilicsurface state is a superhydrophilic surface.
 21. The method of claim 14,further comprising removing at least a portion of the contamination fromthe contaminated surface.